Tucson is the second-largest city in Arizona and the seat of Pima County. It is located in the southeast part of the state on the Santa Cruz River.

The site was originally settled by the prehistoric Hohokam Indians (300 B.C.–A.D.1400s). The first Europeans to visit the area were Spanish missionaries in the 17th century. In 1700, the Jesuit missionary explorer Father Eusebio Francisco Kino founded the mission of San Xavier del Bac close by the Papago Indian village of Stjukshon (later called Tucson). Stjukshon is an Indian word meaning “village of the dark spring at the foot of the mountain.” The Papago Indians are descendants of the ancient Hohokam peoples.

In 1776, Spanish colonists from Mexico constructed a presidio (fort) at Tucson as protection against the hostile Apache Indians and also established the mission of San Jose de Tucson nearby. Tucson remained a military outpost under Spanish and later Mexican control until the area was sold to the United States as part of the Gadsden Purchase in 1853. Tucson was the capital of the Arizona Territory from 1867 to 1877. It was incorporated as a city in 1877. The town grew rapidly when the Southern Pacific Railroad arrived in 1880 and silver and copper deposits were discovered nearby.

Tucson is a popular vacation and health resort due to its sunny, mild, dry climate and unique desert location. Tourism is important to the city's economy. Major industries include aerospace and missile production, high technology, optics, biotechnology, environmental technology, software, and electronics. Tucson is also the commercial center for the surrounding area's agricultural and mining industries. The city is the home of the University of Arizona.